At the turn of the 17th century, when Shakespeare’s comedy “Twelfth Night” was first put on, actors’ craft was quite different than it is today.

There weren’t really rehearsals or directors. Actors learned their parts on their own, then came together the morning of a show to run through songs, dances and fight scenes.

They carried scrolls with just their lines and cues, not the entire script, and a prompter stood on stage to help as needed. Most performances took place outdoors amid simple sets.

The Original Practice Shakespeare Festival tries to re-create this for audiences.

“We perform in the way we believe Shakespeare’s actors did,” said Brian Allard, a former Vancouver resident and founder and artistic director of the Portland-based nonprofit troupe.

This is the festival’s third season, and its main production is “Twelfe Night.” The troupe uses the First Folio text, so certain words are spelled differently than expected (“Twelfe Night” instead of “Twelfth Night,” for example).

The troupe has been performing throughout the greater Portland area all summer, and will be at Esther Short Park on Aug. 20. The show begins at 2 p.m. and lasts between two and two-and-a-half hours, depending upon interruptions.

Shows take place on the grass in front of two tents. People of all ages, Shakespeare fans and nonfans alike, can appreciate the accessible, energetic, physical style of the performances, Allard said.

“Twelfe Night,” like several Shakespeare plays, revolves around issues of mistaken identity.

It’s about Sebastian and Viola, twin brother and sister, who are separated in a shipwreck, Allard said. “Both believe the other to be dead. They end up in the same city. The woman dresses up like a man, so she and her brother keep getting mistaken for each other and people fall in love with them not knowing what’s going on.”

There’s also a subplot involving a group of pranksters.

“There are some pretty crazy characters in it, and the mistaken-identity stuff gets pretty funny and silly,” Allard said.

When the show was first staged in the early 1600s, men played all the roles. For his production, Allard has male and female actors but employs gender-blind casting. So, depending on the performance, a male actor might play the female character Viola, who then masquerades as Cesario, a man.

Allard got the idea for the Original Practice Shakespeare Festival from his experience performing with the New England Shakespeare Festival, which presents the Bard’s work in the original, Elizabethan style.

He was also inspired by the “Secrets of Acting Shakespeare: The Original Approach,” a book by Original Shakespeare Company co-founder Patrick Tucker.

The Original Practice Shakespeare Festival has a main cast of 13 actors from the Portland area, as well as two guest artists from outside the Northwest, an alternate cast of 13 actors, and three interns.

Each actor learns three or four roles and finds out which part he or she will play the morning of the show. Allard meets with all the actors individually to make sure each has a good understanding of the text, but otherwise they’re on their own to prepare.

Changing up the cast helps make every performance feel like the first time. It’s also a fun, albeit nerve-wracking, challenge for the actors, who memorize their parts but can fall back on scrolls and the prompter.

“This is terrifying for most actors,” Allard said.

He would know, since he’s part of the main cast. For the Vancouver production of “Twelfe Night,” he’ll be the prompter. In addition to helping actors with lines if needed, the prompter acts as a moderator of sorts and dresses like a referee, complete with a black-and-white striped shirt and a whistle.

Because the productions take place outdoors in public parks, disruptions often occur. If need be, the prompter will stop the action and help entertain the audience until the show can resume.

These unexpected elements help add to the overall off-the-cuff feel of the show, as does the audience interaction.

“We always tell audiences they should throw all the rules of audience etiquette out the window,” Allard said.

People who attend Original Practice Shakespeare Festival productions are encouraged to cheer, boo and yell. This is in keeping with the theater-going experience during Shakespeare’s time, when audiences were very vocal and boisterous, Allard said.

Since its founding, Original Practice Shakespeare Festival has performed “Much Adoe About Nothing” and “A Midsommer Nights Dreame,” in addition to “Twelfe Night.”

All three of those plays are comedies. Next year, Allard plans to branch out into tragedies with “The Tragedie of Romeo and Juliet.” He’ll also add the comedy “As You Like It,” giving the company a total of five shows. The plan is to perform all of them on five consecutive days next summer.

Allard meets with the troupe’s core members several times a month throughout the year to help them hone their craft. He feels that the company is finally ready to tackle a tragedy, which isn’t as natural a fit for their performance style as comedies.

“This style plays very well with comedies,” he said. “It’s light and fast and fun and silly. There’s a lot of audience interaction, playing with the audience. It’s very broad style.”